This invention relates to an apparatus for delivering and distributing powdered materials over a surface. More particularly, it relates to the charging of a furnace eg. for the production of molten glass, with silica and the like by distribution of such materials over the upper surface of the melt. As a specific embodiment, the invention relates to a conveyor feed system that is configured to occupy a reduced floor area within a melt-shop. As a further embodiment the feed system is configured to deliver its charge while it is, itself, being refilled.
In furnaces of the continuous feed type, particularly glass melters operating on a cold top basis, the charging of raw materials into the crucible must be effected in a controlled and evenly distributed manner. In glass furnaces, silica, lime and other components are continuously distributed over the top surface of the melt so as to provide a heat-conserving, insulative, upper layer floating on the melt. The level of this layer should be closely controlled to provide proper furnace operation. By adjusting the flow of current to electrodes within a furnace, the thickness and the rate of melting of the non-melted top-insulating layer should be maintained within target values over the entire top surface of the furnace. If the furnace has hot spots where melting is more rapid the rate of charge for such areas should be adjusted to maintain blanket thickness.
A consideration in the design of chargers for furnaces is the floor area available for operating the furnace. Most chargers extend outwardly beyond the periphery of the furnace, consuming valuable floor space. With longitudinally feed systems such as screw and belt conveyors, the external space occupied by the charger can approach and exceed the width of the top surface of the furnace. This situation arises from the need to extend and retract the screw or conveyor so that its discharge end can be located over all portions of the upper surface of the melt.
Chargers of this type can be located on a pivot to permit the discharge end of the conveyor to swing over the width of the topside surface. Or they may be mounted on a rail providing transverse displacement of a charger having a fixed orientation with respect to the furnace crucible. In either case, providing access to the full area of the topside surface of the melt is an essential requirement.
The extension of such charging apparatus over floor space adjacent to the furnace consumes valuable plant real estate. It would be highly desirable to provide a furnace charger, which is able to feed materials over the entire topside surface area of a furnace without consuming a substantial amount of floor area adjacent to the furnace. This invention addresses that objective.
A further concern in this art is the time that a conveyor spends in charging a furnace. Typically, conveyor systems carry an on-board supply of charging materials in a bin that must be refilled periodically. To refill this bin, such conveyor systems are moved to a refilling station. Presently, attendance at such a refilling station is xe2x80x9cdown-timexe2x80x9d when the conveyor is not engaged in charging the furnace. A further object of the present invention is to reduce the proportion of down-time arising from refilling an on-conveyor supply bin.
The invention in its general form will first be described, and then its implementation in terms of specific embodiments will be detailed with reference to the drawings following hereafter. These embodiments are intended to demonstrate the principle of the invention, and the manner of its implementation. The invention in its broadest and more specific forms will then be further described, and defined, in each of the individual claims, which conclude this Specification.
According to the invention in one aspect, a charger for a furnace having a crucible with a topside surface over which is to be distributed charging materials includes a belt conveyor with a discharge end supported by a telescopic boom as part of a telescopic conveyor assembly. The charger is positioned on support means located along the periphery of the surface to be charged. This support means may comprise a pivoting base that allows the discharge end of the conveyor to be positioned over substantially the entire or greater part of topside surface to be charged. Or it may comprise a carriage mounted on a rail for moving the conveyor boom transversely along the periphery of the furnace. Such rotational or translational displacement combined with the extension and contraction of the telescopic boom enable the discharge end of the belt conveyor to be positioned over substantially the entire top surface of the furnace which is to be charged to the extent required for cold-top furnace operation.
To minimize the footprint of floor space adjacent to the furnace occupied by the charger, the conveyor belt along the periphery of the furnace is redirected vertically by a vertical take-up system. Thus the belt has a horizontal run for the greater part of the span of its extent over the surface of the melt; and a vertical extent for the length of its vertical take-up. Conveniently, the vertical take-up over-lies or is adjacent to the support means on the side remote from the furnace, limiting the extent to which the conveyor charger assembly extends horizontally beyond the furnace periphery when its discharge end is retracted to a position near to the support means. As the boom for the horizontal extension of the conveyor is telescopic, the extension of components of the charging system over valuable floor space is minimized when the conveyor is in its retracted position.
The belt take-up system may carry the taken-up portion of the belt in a generally vertical direction, while still tensioning the belt, (which is intended to be still running during take-up), through the use of weights, powered cylinders or the like which serve as tensioning means. Alternatively or additionally, the belt take-up system can impose on the belt a sinuous path of optionally variable amplitude, shortening the overall height of the belt take-up system.
The belt take-up system need not be located centrally over the support means. Allowing that it is desirable to counter-balance the torque on the support means that arises from the boom, particularly in its extended state, the belt take-up system can be located outwardly from the center of the support means. This will provide a counter-torque reducing the torque developed by the boom on the support means.
As one of the objects of the feed system is to provide for a continuous charging operation, a supply bin for the conveyor, carried by the charger system, may be replenished at regular intervals from a fixed supply silo source. Access to the supply silo can be intermittent so long as the on-charger supply bin is sufficiently filled to provide charge continuously to the conveyor. By providing a pivoting support means such recharging access to the supply silo can be made conveniently available when the charger is in a specific location. Thus refilling of the supply bin can occur while the telescopic boom is engaged in extending or contracting and/or pivoting in the course of distributing a charge over the melt.
In the case of a charging system relying on a rail-supported travelling carriage moving along one axis -y- as the support means, two reloading stations with two supply silos may be provided. These may be provided at the two outer ends of the carriage tracks. Replenishment of the on-charger supply bin can thereby be effected while the furnace is being fed from either one of the ends of the carriage tracks.
Combined with a charging system incorporating a pivoting support means, two such end-located silos may recharge the on-charger supply bin while the pivoting support means is delivering a charge over virtually all of the surface of the melt. In this manner xe2x80x9cdown-timexe2x80x9d is minimized to nearly its absolute limit.
The foregoing summarizes the principal features of the invention and some of its optional aspects. The invention may be further understood by the description of the preferred embodiments, in conjunction with the drawings, which now follow.